Information broadcast systems include subscription-based systems in which a user subscribes to a broadcast system that provides programming or other content to the subscriber through a cable network or a satellite dish, for example. Since the programming is broadcast, it is transmitted once for receipt by all eligible receivers. Access to the data, however, is conditional, depending, for example, on whether or not a subscription fee has been paid for a specific receiver. Such conditional access to the content is realized by encrypting the information (usually the encryption occurs in the transmitter) under control of an authorization key and by transmitting the encrypted content to the receivers. Furthermore, the decryption keys necessary for the decryption of the content are encrypted themselves and transmitted to the receivers. Often, symmetrical encryption techniques are used, where the encryption and decryption keys are the same. Only those receivers that are entitled to the content are able to decrypt the decryption key using a first decryptor. The receivers can then decrypt the content using a second decryptor for decrypting the content under control of the authorization key.
Conditional access is provided by conditional access (CA) systems that come as matched sets—one part is integrated into the cable system headend (in a cable broadcast system) and encrypts premium content, the other part provides decryption and is built into the set-top boxes installed in user's homes. Several CA systems are used in the cable industry, including those provided by Motorola (Schaumberg, Ill.), Scientific Atlanta (Atlanta, Ga.) and NDS (Staines, U.K.).
To receive encrypted services a user needs a set-top box for each and every television in his or her residence. Each set-top box must be connected to the cable or satellite system over which the multi-service operator (MSO) provides programming. The more televisions a user has, the more set-top boxes that are required. The only exception today is in cable systems that offer some analog TV channels in the clear (i.e. unprotected). Any television built in the last 20 years can receive such channels directly (i.e., without a set-top box). Without the set-top box, however, such a television could of course only receive analog channels, but most MSOs offer upwards of 80 such channels today.
Long term, these MSOs would prefer to reclaim all currently transmitted analog television channels and replace them with far denser compressed digital services. Unfortunately, a completely digital television system means that the consumer needs a set-top for every television he or she has in the home. This requirement has intensified focus on lower and lower cost set-top boxes, and has also contributed to the drive towards televisions that are digital cable ready, that is, with set-top technology inside them.
Recently, a new architecture has emerged that would avoid the need for a set-top box per television. In this architecture the system operator installs a terminal on the side of the residence, in the path of the cable feed to the residence. The terminal receives the 80 digital channels supplied by the MSO and converts them to 80 analog channels that are modulated conventionally on the in-home coax. The MSO thus has the benefit of carrying all channels in a digitally compressed format, allowing more total services and revenue, while the residence would appear as it does today, with 80 analog channels feeding as many in-home televisions as the user wishes. No set-top boxes would be required until the consumer wished to access encrypted content such as premium programming (e.g., HBO™) or video-on-demand, for example. The user would not even be aware that the residential-side terminal was present, since no special in-home equipment is required and there would be no direct user interaction with the terminal.
A multiple service, residential-side terminal would need to tune, demodulate, decode, and output (as an analog RF signal) many programs simultaneously. Currently, the number of programs might be as high as 80 or more for many cable systems. Proponents of such an arrangement need to find techniques for efficiently performing these various processing steps on such a large number of programs at reduced cost. After all, an architecture requiring a set-top box per television would be the least expensive and therefore the preferable approach if a residential-side terminal were too expensive. Schemes are currently in development for tuning, demodulation, decoding, and upconversion that hold the promise of performing these functions at a reasonable cost. In the case of decryption and CA, residential-side terminal proponents are considering totally new approaches that may be incompatible with (and less secure than) legacy CA systems that are currently deployed in set-top boxes.
Accordingly, it would be desirable to provide a method and apparatus for providing conditional access that is compatible with existing conditional access schemes employed in set-top boxes and which can also serve to simultaneously decrypt all the channels that the subscriber is entitled to access so that a complete set of analog channels can be provided to the various televisions in the user's residence, at low cost and complexity.